Multiple basic carboxypeptidases (CP) have been detected in diverse tissues and cells. This group of CP are metalloproteases that perform a wide variety of cellular functions. One of the basic CP that has received considerable attention has been CPH (E.C.3.4. 17. lO), due its proven role in the processing of neuropeptides and the availability of the specific inhibitor GEMSA. Our laboratory has recently contributed in the characterization in bovine and rat brain of a novel CP, with biochemical properties diametrically opposed to CPH. This CP is Insensitive to GEMSA, Inhibited by cobalt, its activity Increased by A-kinases I, II, and has an alkaline pH optimum. We have demonstrated that the originally proposed name ("processin CPE") for the enzyme expressed in brain cytosol is a misnomer since enkephalins are not its only substrates, and it is expressed in a vesicular population different from those transporting CPH and neuropeptides, consequently we have renamed it CPI. This proposal specifically aims to isolate and purify the soluble and membrane bound forms of CPI from bovine brain, and to perform the biochemical characterization of the purified enzyme (kinetic properties, membrane- anchoring mechanism, effects of ions, inhibitors and activators). In addition, immunological probes (polyclonal antibodies) will be generated against the purified CPI forms in order to determine its patterns of expression in diverse tissues, cells and subcellular organelles. Carboxypeptidases have been proposed to play a role in fundamental physiological processes; such as, proteolytic maturation of neuropeptides, inactivation of hormones, shifting the receptor selectivity spectra of neuropeptides, and the biochemical modification of proteins and enzymes. In addition, they have been proposed to participate in the pathophysiology of neurodegenerative disorders, vascular degenerative disorders, ischemia, viral and tumor invasion. A future project will ultimately endow us with the capability and necessary immunological probes for the conduction of studies aimed towards the elucidation of the expression and role of CPI in the above fundamental physiological processes and pathophysiological conditions.